PST1 and ECM33 encode two yeast cell surface GPI proteins important for cell wall integrity

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Pst1p, a secreted yeast protein, is implicated in cell wall construction.
• ECM33 encodes a protein homologous to Pst1p, sharing GPI-anchored protein features and an L-domain.
• Both Pst1p and Ecm33p are localized to the yeast cell surface.

Purpose of the Study:

• To characterize the roles of Pst1p and Ecm33p in yeast cell wall integrity.
• To investigate the functional relationship between Pst1p and Ecm33p.
• To elucidate the impact of their deletion on cell wall structure and viability.

Main Methods:

• Generation and analysis of pst1Delta, ecm33Delta, and pst1Delta ecm33Delta yeast mutants.
• Assessment of cell wall integrity and ultrastructure.
• Analysis of Slt2p activation (MAP kinase pathway).
• Examination of glycosylated protein defects.

Main Results:

• Deletion of ECM33 results in a weakened cell wall, exacerbated by PST1 deletion.
• The ecm33Delta mutant shows increased Slt2p activation and requires the cell integrity pathway for viability.
• ECM33 deletion causes glycosylation defects and disrupts cell wall ultrastructure and mannoprotein assembly.
• Pst1p appears to function in a compensatory mechanism during cell wall damage, partially substituting for Ecm33p.

Conclusions:

• Ecm33p is essential for yeast cell wall organization, mannoprotein assembly, and glycosylation.
• Pst1p plays a compensatory role, particularly under conditions of cell wall stress.
• The interplay between Pst1p and Ecm33p is critical for maintaining cell wall integrity in yeast.